Device qualification for DSBGA (Die-Sized Ball Grid Array), WCSP (Wafer Chip Scale Package), QFN (Quad Flat No lead) and other semiconductor devices involves electrical and reliability testing of a predetermined number of prototype devices that have been produced at a particular facility. There are number of occasions during device qualification in which physical handling of a device occurs. For example, loading of a semiconductor device (sometimes referred to herein as a “DUT,” “device under test,” or simply “device”) into various test equipment, such as ATE (automatic test equipment) biased reliability test equipment, such as B-HAST (Biased Highly Accelerated Stress Test), Autoclave, etc., and removing the device from such equipment all require handling of the device. However, handling of a device may cause catastrophic damage, chipping or loss of the device (especially with small and extremely small die sizes). Handling may thus cause qualification failures that are not related to the quality of the device.
A number of reliability tests require stressing of a device under bias. The current technique for doing this involves mounting the device (typically by soldering) on a conversion printed circuit board (PCB). The device mounting process includes a number of cleaning and processing steps, which have inherent risk of damaging the device before the bias reliability test is even conducted. If the device fails any of the bias reliability tests, separate failure analysis testing of the device must be performed. In the event of bias reliability test failure, the device must be removed from the PCB and cleaned to remove solder flux before failure analysis on the device is conducted. These process steps required after reliability test failures, introduce further opportunities for handling-related device failures.
In addition to the risk of handling-related failures there are other problems inherent in current device qualification procedures. Variations in the printed circuit boards on which devices are mounted for testing introduce a separate set of variables. These variables include: the type of board material that is used; design variations between boards; the type of flux used to attach a device to a conversion board; and variations in the cleaning process used for flux removal.